2) The spray foam unventilated ceiling. I live in a colder area than you, and did not fully research hot roofs, but there is a limit to where they work.. I was under the impression where I am it is probably too cold. The surface of your roof will be warm when snow is on it... if it is above 32F you could end up with some ice damming. A lot of this concern also goes away with it not being continuously heated all winter.
Thickness: I don't know how much help I will be getting for getting the roof sheathing up there. I plan on hauling the sheathing up to the loft, and then sending out the "holes" where the dormers are going (except of course, for the dormers' sheets themselves). Still, it will be a heavy lift, litterally. Table R503.2.1.1(1) seems to indicate I could go with 1/2-inch sheathing, even without edge support with my 24" spacing, and I may have some 1/2-inch panels left over from the wall sheathing. Nathan, I know you put 5/8" on even with 16" spacing, so I suspect the advice is go with 5/8".
Material: I am glad I am going with the zip system for the walls as I can't imagine trying to get tyvek up there by myself. For the roof, I am not sure. The advantage of going with zip for the roof is that it doesn't need the tar paper, but even if I go with the vents, I think at least one row of adhesive barrier would probably be needed. Does the zip system really obviate the need for tar paper?
Note, I am probably going to contract out the actual installation of the steel roof, mainly for safety concerns, and secondarily to make sure it is done right (although I have had zero problems with my shed's roof, but it was much smaller). There will probably be a delay between when I get the sheathing on and when the roofer shows up to install the roof. With this delay maybe it makes more sense to use the zip since I don't plan on putting the tar paper on myself, again due to safety concerns.
If I don't go with zip, would plywood be a better choice than OSB if there is an interval between the sheathing and the roofing?
Does the T&G zip cause those sheets to be 47.5" like the advantech flooring? That could be a probably with my system designed for multiples of 4'
Thanks in advance for any and all suggestions.
Getting the sheathing up there was an awful job. I used C clamps as handles. I put all the sheathing on alone, instead of dormers I had one rafter bay spaced at 24" for the chimney. Slid it out with C clamps for handles, and also clamped stop blocks on the fascia so that the first course would automatically slide into position. I nailed in as much as I could from within the attic, then climbed out on top to finish it off. The T&G likely did shrink the 48" to 47.5", if that's an issue. Without T&G I think you will need to fiddle with H clips.. I really liked that for such an awkward one person job it was one less thing to worry about.
Nothing wrong with going with the lightest stuff that is rated for 24" rafters.
I found the sheathing to be a lot more work, and similarly dangerous, to installing the metal.
I put on ice and water shield, in retrospect it was unnecessary. In my bulk order I had included it (had it on hand, and figured why not) because I thought the code required it, but I'm pretty certain it's only required for shingles.
The ice and water shield was pretty grippy, but nothing is as easy to walk on as zip - a huge advantage. Also really easy to use the tape. And if you don't get the steel on this year, you can feel confident that tape can handle a NY winter... that is not true of any other waterproofing that I know of.
If you were installing an unvented roof, I would probably say to use ice and water shield. Ice damming could put the nail holes under hydrostatic pressure which might actually leak.
One last thought, if you vent using furring strips on top the roof, you essentially are building a lattice, giant ladder, to crawl around on. What Mike 870 did except without the insulation. If you go that route, that would be pretty safe/comfortable in my opinion.
Always wear a harness and make sure the slack is short enough that if you fall you will not drop over the eave.
So yes I do agree with that part of the article, pay attention to your zone and be there, absolutely be there, with your straightend coathanger with tape at the agreed upon depth and thump their work often with it. If you can't afford to take a day off to be there I'd say you can't afford to risk it, go all foam.Thanks. I would definitely take the day off and be there when they do it.
I think that was a rant :D
I am not too familiar with rescheck, I wound up doing everything in excel. What an impact air tightness has... not to mention the importance of thermal bridging from studs and windows. U-factor is a better measure but I guess builders don't like decimals.
I would think the assembly R-value of the flash+batt would be around 40, just batt around 35, and batt+2" of XPS 45 - cheaper than flash+batt but more work and time. The flash+batt would also be air tight. Ceiling air tightness is critical because of buoyant hot air.
I have not had a good experience with Andersen windows. I have at least one that leaks some how, and when I pulled it to figure out what was going on, I leaned it upside down and water poured out of the miter joints. One of the few benefits of how slowly I've been building is that I've gotten to stair at rough sills for close to 2 years now.
Separate question: the "design for code compliance" guide for decks (https://www.awc.org/pdf/codes-standards/publications/dca/AWC-DCA62012-DeckGuide-1405.pdf) says that diagonal braces only go out the out-most posts, and are actually prohibited for the posts in the middle. Does anyone know the reason for this?
Diagonal bracing can contribute to the stiffness of the deck and, therefore, cause additional lateral loads on the posts. Since center posts receive more vertical load than corner posts, additional lateral load can cause overstress. For this reason, DCA 6 does not show the use of diagonal bracing on center posts.
The roof looks nice, I'm sure it's a relief to have that done. Based on October and November (so far) it seems like it's gonna be a damn cold winter.
If I understand the window question right, it sounds like ideally you would have brought the window buck extensions out another 3/4" installed the windows, flashed everything, then butt the 1x6 up against that?
If it was me, I would remove the 1x6, cut the foam back a bit, install the window, tape the window flange to the window extension, the tape extending all the way back and connecting to the zip wall, then I'd put the foam and furring strips back on.
On the dormers since I think you're talking about making the foam the water barrier, you could remove the 1x6, install the window, tape the flange to the foam.
Recessed windows does mean jamb extensions...
after I posted I tried to edit - what about extending the jamb out an extra .75". You'd be glad when it is time to do siding that you don't have to do the jamb extensions.
This was a pretty terrible year weather-wise. We were getting snow on April 30th.. I was hoping it would balance out with a decent fall, but as soon as Oct 1 came we went straight from the 60s to the 40s.
And it has been unbelievably wet over here too. Our fields are like a swamp, but as of today it's been so cold I think it's starting to freeze up..
If you did extend the jambs 3/4", you should have king studs next to the window that you can use structural screws to attach the furring strips.
Just wanted to say thanks for documenting this build so well, AND your thought process as you move along. Good to see what you're thinking about and what decisions you're making along the way.
I ordered two sets of the 3-5/8" Jamsills direct. They were very helpful.
The Andersen instructions say to install a drip cap, but I can't seem to find them. I think they put that in their instructions so they have an excuse to void the warranty if they leak. I figure the first row of tape along the top of brickmould serves that purpose. No one will ever be looking down onto the brickmould.